Process for the production of matt epoxy resin and hybrid powder coatings

Abstract

A curing agent for a composition useful for the production of matt epoxy resin and hybrid powder coatings, comprising a mixture of a) salts of phthalic acid, isophthalic acid and terephthalic acid with the following amines ##STR1## in which R 1 , R 2 and R 3 are identical or different aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radicals having 1-20 carbon atoms and in which one or more CH 2 groups in the carbon chain may be replaced by 0 atoms, by NR 4 groups where R 4 =C 1-6 -alkyl, CH--OH groups, and/or one or more terminal methyl groups may be replaced by dialkyl-substituted amino groups having 1 to 6 carbon atoms, and R 1 and R 2 may form a joint ring in which one CH 2 group may be replaced by an O atom or by an NR 4 group, and R 1 =R 2 =R 3 --CH 2 --CH 2 -- attached via a common nitrogen atom, and n=3-11, and 0.5-2 mol of amine A)-C) per mole of acid, and b) pyromellitic acid and/or trimellitic acid, 0.25-2 mol of b) being employed per mole of a).

What is claimed as new and desired to be secured by letters patent of the United States is: 
     
       1. A curing agent for a composition useful for the production of matt epoxy resin and hybrid powder coatings, comprising a mixture of a) salts of phthalic acid, isophthalic acid and terephthalic acid with at least one of the following amines ##STR3## in which R 1 , R 2  and R 3  are identical or different aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radicals having 1-20 carbon atoms and in which one or more CH 2  groups in the carbon chain may be replaced by 0 atoms, by NR 4  groups where R 4  =C 1-6  -alkyl, CH--OH groups, and/or one or more terminal methyl groups may be replaced by dialkyl-substituted amino groups having 1 to 6 carbon atoms, and R 1  and R 2  may form a joint ring in which one CH 2  group may be replaced by an O atom or by an NR 4  group, and R 1 , R 2 , R 3  =--CH 2  --CH 2  -- and n=3-11, and 0.5-2 mol of amine A)-C) per mole of acid, and   b) pyromellitic acid and/or trimellitic acid, 0.25-2 mol of b) being employed per mole of a).   
     
     
       2. A composition useful for the production of matt epoxy resin and hybrid powder coatings, comprising a mixture of: an epoxy resin, optionally a polymer which contains carboxyl groups and the curing agent of claim 1.   
     
     
       3. The composition of claim 2, wherein the concentration of curing agent ((a)+(b)) in the powder formulation is 3-14% by wt., based on the sum of epoxy resin plus the polymer which contains COOH groups. 
     
     
       4. A process for the production of matt epoxy resins and hybrid powder coatings, comprising: applying the composition of claim 1 to a substrate, and   heating the applied powder composition thereby forming a matt finish.   
     
     
       5. The process of claim 4, wherein the applied powder coating is heated to 150°-220° C. for 30 secs-8 min.